From: xu xin <[email protected]>
In /proc/<pid>/ksm_stat, Add two extra ksm involvement items including
MMF_VM_MERGEABLE and MMF_VM_MERGE_ANY. It helps administrators to
better know the system's KSM behavior at process level.
KSM_mergeable: yes/no
whether the process'mm is added by madvise() into the candidate list
of KSM or not.
KSM_merge_any: yes/no
whether the process'mm is added by prctl() into the candidate list
of KSM or not, and fully enabled at process level.
Changelog
=========
v1 -> v2:
replace the internal flag names with straightforward strings.
* MMF_VM_MERGEABLE -> KSM_mergeable
* MMF_VM_MERGE_ANY -> KSM_merge_any
Signed-off-by: xu xin <[email protected]>
---
fs/proc/base.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 18550c071d71..50e808ffcda4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3217,6 +3217,10 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages);
seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
+ seq_printf(m, "KSM_mergeable: %s\n",
+ test_bit(MMF_VM_MERGEABLE, &mm->flags) ? "yes" : "no");
+ seq_printf(m, "KSM_merge_any: %s\n",
+ test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no");
mmput(mm);
}
--
2.15.2
On 26.04.24 03:46, [email protected] wrote:
> From: xu xin <[email protected]>
>
> In /proc/<pid>/ksm_stat, Add two extra ksm involvement items including
> MMF_VM_MERGEABLE and MMF_VM_MERGE_ANY. It helps administrators to
> better know the system's KSM behavior at process level.
>
> KSM_mergeable: yes/no
> whether the process'mm is added by madvise() into the candidate list
> of KSM or not.
> KSM_merge_any: yes/no
> whether the process'mm is added by prctl() into the candidate list
> of KSM or not, and fully enabled at process level.
>
Thinking about it, we should avoid exposing internal toggles with
unclear semantics to the user. See below.
> Changelog
> =========
> v1 -> v2:
> replace the internal flag names with straightforward strings.
> * MMF_VM_MERGEABLE -> KSM_mergeable
> * MMF_VM_MERGE_ANY -> KSM_merge_any
>
> Signed-off-by: xu xin <[email protected]>
> ---
> fs/proc/base.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 18550c071d71..50e808ffcda4 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -3217,6 +3217,10 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
> seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages);
> seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
> seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
> + seq_printf(m, "KSM_mergeable: %s\n",
> + test_bit(MMF_VM_MERGEABLE, &mm->flags) ? "yes" : "no");
All it *currently* means is "we called __ksm_enter()" once. It does not
mean that KSM is still enabled for that process and that any VMA would
be considered for merging.
I don't think we should expose this.
That information can be more reliably had by looking at
"/proc/pid/smaps" and looking for "mg".
Which tells you exactly if any VMA (and which) is currently applicable
to KSM.
> + seq_printf(m, "KSM_merge_any: %s\n",
> + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no");
This makes more sense to export. It's the same as reading
prctl(PR_GET_MEMORY_MERGE).
The man page [1] calls it simply "KSM has been enabled for this
process", so process-wide KSM compared to per-VMA KSM.
"KSM_enabled:"
*might* be more reasonable in the context of PR_SET_MEMORY_MERGE.
It wouldn't tell though if KSM is enabled on the system, though.
[1]
https://lore.kernel.org/linux-mm/[email protected]/T/
--
Cheers,
David / dhildenb
>> @@ -3217,6 +3217,10 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
>> seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages);
>> seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
>> seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
>> + seq_printf(m, "KSM_mergeable: %s\n",
>> + test_bit(MMF_VM_MERGEABLE, &mm->flags) ? "yes" : "no");
>
>All it *currently* means is "we called __ksm_enter()" once. It does not
>mean that KSM is still enabled for that process and that any VMA would
>be considered for merging.
>
>I don't think we should expose this.
>
>That information can be more reliably had by looking at
>
>"/proc/pid/smaps" and looking for "mg".
>
>Which tells you exactly if any VMA (and which) is currently applicable
>to KSM.
>
>
>> + seq_printf(m, "KSM_merge_any: %s\n",
>> + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no");
>
>This makes more sense to export. It's the same as reading
>prctl(PR_GET_MEMORY_MERGE).
>
>The man page [1] calls it simply "KSM has been enabled for this
>process", so process-wide KSM compared to per-VMA KSM.
>
>"KSM_enabled:"
>
>*might* be more reasonable in the context of PR_SET_MEMORY_MERGE.
>
>It wouldn't tell though if KSM is enabled on the system, though.
>
I agree it. But I hope admistrators can tell if the process enabled KSM-scan
by madvise or prctl. At this point, only "/proc/pid/smaps" is not enough.
So can we add a item "KSM_enabled" which has three value as follows?
1) "prctl": KSM has been fully enabled for this process.
2) "madvise": KSM has been enabled on parts of VMA for this process.
3) "never": KSM has been never enabled for this process.
Just refer to the semantics of '/sys/kernel/mm/transparent_hugepage/enabled'